A lubricant for lubricating the interface between two surfaces intended to move relative to one another must meet a number of requirements to be useful. The lubricant must be essentially chemically and physically inert with respect to both surfaces. The lubricant must sufficiently reduce the force required to move one surface past the other. And, the lubricant must be in a form that permits easy application of the lubricant to one or both surfaces.
The first of such lubricants were composed of natural fats and oils typically thickened with clay or chalk. With the advent of the petroleum industry lubricating oils and greases were prepared from heavy petroleum fractions. The petroleum based lubricating oils offered many advantages over prior lubricants and in many application are still the lubricant of choice. However, in many applications petroleum based lubricants are undesirable as they can adversely interact with many substances such as plastics and rubbers, can be difficult to clean up, can remain in place well after application and can be unpleasant to workmen.
In view of the drawbacks which petroleum based lubricants present in certain applications, water based lubricants were developed. Many compounds have been used in preparing aqueous lubricants such as high molecular weight polyalkylene oxide polymers, fatty acid soaps, acrylate polymers, waxes, alkylene glycols, guar gum, Irish moss, carboxymethyl cellulose, phenolic and amine-formaldehyde resins, hydrocarbon sulfonic acids, gelatin, polyurethanes, borax, and others. See for example U.S. Pat. Nos. 2,958,659; 3,227,652; 3,699,057; 3,925,216; 4,111,800; 4,111,820; 4,461,712; and 4,522, 733. Aqueous based lubricants are generally less reactive, easier to clean, easier to apply and more agreeable to use than petroleum based lubricants.
To the best of my knowledge aqueous based lubricants containing many of the above mentioned compounds can suffer certain disadvantages. The lubricant compositions can be stiff, can be nonthixotropic, can be hard to handle and apply to the surface, can fail to sufficiently reduce the coefficient of friction under a broad load range, can fail to provide sufficient dry lubrication to facilitate subsequent movement of the surfaces relative to one another, can bond the surfaces together upon drying, can adversely interact with many substances and can be expensive.
Accordingly a need exists for an inexpensive substantially inert aqueous lubricant that can be easily handled, easily applied, easily cleaned, provide effective lubrication both before and after drying and provide a low coefficient of friction under heavy or light load.